Gating circuits for electrical musical instruments



Feb. 1, 1966 w. MUNCH, JR., ETAL 3,233,031

GATING CIRCUITS FOR ELECTRICAL MUSICAL INSTRUMENTS Filed June 27. 1960 3 Sheets-Sheet 1 Z 6 2 7 AUDIO aecrwmc AUDIO [LECI'EOTCI L sou/2c l i VALVE 067E702] Luz/2%? VALVE OUTPUT 1 a1 1 1, 6; T T o. c. I 2. F? L 2. F. /6 Lac. er. souece 2.2 Souece souece I FILTER sou/ace {Enamel F/LTEE 1 .1. 7 EGZ.

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Feb. 1, 1966 w. MUNCH, JR., ETAL 3,233,031

GATING CIRCUITS FOR ELECTRICAL MUSICAL INSTRUMENTS 3 Sheets-Sheet 2 Filed June 27, 1960 TONE COLOIZ s Vs TEM OUTPUT SYSTEM FIG. Z

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Feb. 1, 1966 w. MUNCH, JR., ETAL 3,233,031

GATING CIRCUITS FOR ELECTRICAL MUSICAL INSTRUMENTS 3 Sheets-Sheet 5 Filed June 2'7. 1960 INVENTORS. W44 76? Mwvcy, Je. BY Passer C. Sc/mem ATTORN YS.

United States Patent Ofiice 3,233,031 GATING CIRCUITS FOR ELECTRICAL MUSICAL INSTRUMENTS Walter Munch, In, Covington, Ky., and Robert C. Scherer, Cincinnati, Ohio, assignors to D. H. Baldwin Company, Cincinnati, Ohio, a corporation of Ohio Filed June 27, 1960, Ser. No. 38,835 25 Claims. (Cl. 84-1.11)

This. invention has to do with the problem of transferring electrical oscillations from continuously operating sources in an electrical musical instrument to an output system in accordance with the requirements of a musical composition. In instruments comprising continuously operating generators, the use of simple make-andhreak key switches produces an abrupt onset of the tones which is generally undesirable. In order to avoid this there has been Widespread use of gradual contact or resistive key switches; but these are relatively expensive. One of the primary objects of this invention is to provide a gating system for electrical musical instruments in which theonset of the tones is determined electrically so that ordinary make-and-break key switches can be employed.

Another object of the invention is to provide a system for gating oscillations in an electrical musical instrument which will be inexpensive and reliable.

In many instances a gradual onset of the tones is desired and also a gradual decay thereof when the playing. key is released... A gradual decay of the tones more closely simulates the effect of organ pipes; but it has other uses also. Gradual decay may be employed to give a certain efiect of reverberation to the output of the instrument, and in instances where the keys arepl-ayed in a staccato iashion gradual decay may he caused to give the effect of bells, bars, plucked or struck strings and the like-these effects being generally known as percussive effects. object of the invention to provide a gating system for electrical musical instruments which will provide all of the effects of gnad-ual decay of the tones Where desired, and' do so in a simple and inexpensive fashion.

In instruments employing continuously operating generators and electrical gating means, problems of feedthrough are sometimes encountered; and it is. also an important object of this invention to provide a system in which feed-through is avoided.

These and other objects of the invention which will be set cfortlr hereinafter or will be apparent to one skilled in the art upon readingthese specifications, are accomplished by that construction and arrangement of parts on which certain exemplary embodiments will now be described. Reference is made to the accompanying drawings where-- 1n:

FIG. 1 is a block. diagram showing the essential parts of one form of the present invention.

FIG. 2 is another block diagram showing a modified system.

FIG. 3- is in part a circuit diagram and in part a block diagram showing a mode of connection of a continuously operating oscillator and a radio frequency source to a device which acts both. as-a modulator and a valve as in. the system oi. FIG. 1.

FIGS. 3a and 3b are respectively illustrative of modi-- fications of the modulator and valve.

FIG. 4 is partly a circuit diagram and partly a block diagram showing a system in which the valve modulates the radio frequency at the source,,hence detection occurs at the source, as in the system of FIG. 2.

FIG. 4a relates to FIG. 4 but shows the use of athermionic diode in the place of a neon tube.

FIG. 5 is a diagrammatic showing of a system in which the gating circuit provides two successive rates of tone decay.

It is an Patented Feb. 1, 1966 FIG 5a relates to FIG. 5 but shows the use of. the source detection technique.

FIG. 5b relates to FIG. 5 but shows the use of a thermionic diode in the place of a neon tu-be.

FIG. 6 is a circuit diagram detailing one form of gating circuit for a single oscillator in accordance with the organization shown in FIG 1 FIG. 7 is a circuit diagram showing. the circuitry for two oscillators in accordance with the system of FIG. 2.

FIG. 8 is a waveform chart-illustrative of th manner in which the gating circuits of this invention produce a gradual onset of the tones.

FIG. 9 is a diagrammatic showing of a system including a plurality of oscillators and a single radio frequency source.

Briefly, in the practice of the invention a valve elementis employed. To this valve element there is connected a source of audio frequency oscillations, Le, a generator, a source of radio frequency oscillations, and a sourceof direct current. The parameters of the circuits are such that neither the audio frequency voltage nor the radio frequency voltage, nor both are capable of operating the valve- DC. voltage is additionally required for this pur pose; and this makes possible th location in the connection between the DC. source and the electronic valve of a simple make andbreak switch which will be operatedby a playing key of the instrument.

The electronic valve may be a neontube as hereinatter described, in which case the direct current component will b required to raise the potential on the tube toliring potential. The electronic valve may instead be a thermionic diode, in. which case the application of the DC. voltage to the plate circuit will be required to makethediode conductive. Other forms of electrical valves may be employed, the principal requirement being that the impedance of the valve varies- With the amplitude ofthe current through it. Thus, the simultaneous passage ofradio trequency current and audio frequency current through the valve results in the variation inthe conduction of the valve at an audio rate: determined by the gen erator. The amplitude-modulated radio frequency current can then be detected, accordingv to the various forms: of thlSriHVl'ltlOn,.lI1 adesired manner to obtain: theaudio frequency signals corresponding to musical. toneskeyedby thedirectcurrent. In general, the percentage of mod ulationwill be small (1 to 2%), but this amount is easily detectable. Although the percentage modulation available with a vacuum diode is as much as ten times that with a neon tube, the appreciable cost advantage of the latter is-a' tactorfor' consideration. Various methods of detection are possible, and two such. methods are herein"- after set forth.

In FIG. 1 the index numeral 1 indicates" an audio source or generator which is connected to an electronic valve 2. Aradio frequency source 3 is connected tothe electronic valve as is alsoa DC. source 4,. its connection including'a switch 5. The electronic valve is shown con nected on its output side to a detector 6. The detectoroutput has itsradio frequency component filtered out by the R.F-.- filter .16 before being fedinto the output system 7' of the instrument. It will be under-stood that: such am plificationi as is required may be employed the outputsystem 7 and/or between the detector and the output system.

Referring now to FIG. 3 in which like parts-are given like index numerals, the generator 1 is connected: to the electronic valve 2 through a capacitor 8 and a resistor 9-. The DC. source '4 is connected: through the switch 5 and a resistor 10 to the point between the capacitor. 8 and the resistor 9. A capacitor 18' is connected from the junction of the switch 5 and the resistor 10' to the ground 6 return. The generator 1 may be any form of continuously operating generator such as an oscillatory circuit containing -a thermionic tube as set forth in the Jones Patent No. 2,555,038. Other forms of generators may be used including other electrical oscillators, tone wheels, photoelectric generators, etc. In FIG. 3 the electronic valve 2 is a neon tube, generally of some size such as the type NE-2. It is provided with a pair of spaced internal electrodes; and in this instance it is also provided with an external pick-up electrode 11 which coacts capacitively with the electrodes. The electrode 11 may be a thin metal band wrapped about the neon tube and serving, if desired, to support it. It will be noted that the R.F. source 3 is connected to one of the internal electrodes of the neon tube while the generator 1 and DC. source 4 are connected to the other internal electrode. A common return for the generator, the DC. source and the R.F. source is indicated by the ground symbol. As has been indicated above the tube 2 will fire only when the DC. voltage is added to the voltage of the generator and the R.F. source. When the tube fires, its conduction will vary at the A.F. rate of the generator and in this way modulate the radio frequency signal so far as the electrode 11 is concerned. The R.F. source may be any suitable thermionic or other circuit oscillating at a radio frequency rate.

When the switch 5 is closed a modulated R.F. signal will be picked 'up by the electrode 11 and transferred to the detector 6. The capacitor 8 serves a dual purpose. It is not only an audio coupling capacitor but also it controls the DC, voltage build up on the neon tube, thus controlling the onsetof the tone. In other words, when the key switch 5 is closed the capacitor 8, depending on its size, will require a definite time for charging, and the firing potential of the tube 2 will not be reached until the capacitor is charged to a given level since as will be evident from FIG. 3 there is a path to ground through the capacitor 8 and the generator 1. The onset of the tone can be controlled by controlling the size of the capacitor 8. Referring to FIG. 8, in which voltage is plotted against time, the line 12 represents the firing potential of the tube. When the switch 5 is closed the potential on the tube will gradually increase as represented by the saw tooth line 13 which indicates the audio variations of the signal. It should be noted in FIG. 8 that the build up time of the keying voltage appears quite lengthy. This is not the case in a practical situation, but is illustrated here, as such, for the purpose of clarity. Theoretically, with or without the R.F. voltage applied to the other electrode, the tube will fire when the keying voltage exceeds the firing potential. This occurs at the point B and the first few pulsations of the audio signal passing through the electronic valve will gradually increase in amplitude, thus giving the tone onset desired. With the absence of the R.F. voltage, however, some diificulty is experienced in ionizing the tube at point B. This difiiculty is caused by the dark effect which is characteristic of gas dis charge tubes. Consequently the tube fires at some point A where the voltage pulses are high enough to overcome this dark effect, at the same time, however, producing an abrupt onset of the tone. With the R.F. voltage applied, the firing occurs at the point B hence the R.F. signal reduces the dark effect of the neon tube.

A gradual tone decay characteristic is attained, when the key switch 5 is opened, due to the existence of capacitor 18. This capacitor charges instantaneously to the.

D.C. source voltage when the switch 5 is closed and therefore does not affect the tone onset. However, when the switch 5 is opened the charge on the capacitor 18 will tend to maintain the electronic valve in transmitting condition. The charge on capacitor 18 will diminish gradually through resistor 9 and through the valve 2;. This produces a gradual decrease in tone amplitude until such time as the voltage decay becomes less than the extinguishing potential of the tube 2. At this point the tube 2 ceases to conduct and the tone ceases. A gradual or abrupt tone decay is attained by the insertion or rernoval, respectivel of capacitor 18, and the extent of the decay is controlled by the size of capacitor 18.

FIG. 3a shows a mode of obtaining an output signal from the neon tube 2 without the use of an external electrode. What is shown in FIG. 3a may be substituted for what isshown within the dot dash square of FIG. 3; and it will be noted that the connection from the detector may be made through a capacitor 14 to that side of the neon tube to which the generator is connected. FIG. 3b in a similar fashion shows circuitry which can be substituted for the circuitry within thedot dash square of FIG. 3. In FIG. 3b a thermionic diode 15 is substituted for the neon tube 2 and the connection to the detector is made through the capacitor 14 abbve described. The diode 15 will be non-conductive (in the absence of DC. keyed thereto) as will the gas diode 2, since any current tending to flow through the diode 15 will charge up capacitors 8 and 13 in such direction as to bias off the diode 15. That is, current flow through the diode 15 will cause the capacitors to raise the voltage at the junction point between resistors 9 and 10 to a level sufficient to out off the current in the diode 15.

In FIG. 2,'where like parts have been given like index numerals, it will be understood that modulation will take place in the electronic valve 2 when the switch 5 is closed as above described. However, this modulation need not be detected at the valve as in the system of FIGS. 1 and 3. In the system of FIG. 2, the detection is accomplished at the ratio frequency source 3 by a source detector, hereinafter described, which detects audio frequency modulation of the source current being supplied to the valves. A radio frequency filter 16 may be connected with the source detector and with the output system 7. The radio frequency filter will by-pass to ground or the common return the radio frequency component of the sig-.

nal, leaving the audio frequency component for amplification and reproduction. This circuit is shown in a somewhat more detailed fashion in FIG. 4, wherein it will be seen that the connections between the A.F., R.F. and DC. sources to the electronic valve 2 are essentially the same. FIG. 4a indicates that a thermionic diode 17 may be substituted for the neon tube 2. The diode 17 will be be non-conductive '(in the absence of DC. keyed thereto) as will the gas diode 2 for the same reason described above in connection with diode 15.

FIG. 5 illustrates a mode of exercising further control of tone decay. Like parts are again given like index numerals. In this figure the onset of the tone will occur as above described when the key switch.5 is closed, due to the action of the capacitor 8. But it will be noted that the capacitor 18 and a resistor 19 are connected in parallel, beyond the keyswitch, between the negative side of the DC. source 4 and the common return. Also a resistor 2i) and a neon tube 21 (which may be of a type similar to that described above), in series with each other, are connected between the negative side of the D.C. source 4 and the common return. In the circuit of FIG. 5, when the switch 5 is closed the capacitor 18 will charge, and the neon tube 21 will fire. This will not affect the operation of the electronic valve 2 at the time of the onset of the tone. However, when the switch 5 is opened, the charge on the capacitor 18 will tend to maintain the electronic valve 2 in transmitting condition. The charge on capacitor 18 will diminish through resistor 19 and through the neon tube 21 until that tube reaches the extinction potential. This will provide an initial rapid rate of decay. When the tube 21 becomes non-conductive, however, the remaining potential in capacitor 18 will decay much more slowly through resistor 19. In this way the transmitted tone may be caused to decay at two successive different rates, simulating, for example, the mode of decay of piano tones.

The remainder of FIG. 5 is the same as has been de-' scribed in connection with FIG. 1 excepting that a tone color filter 22 has been included. FIG. 5a illustrates the use with the double decay circuit of the type of circuitry described in connection with FIG. 2.

What is shown in FIG. 5b may be substituted for what is shown written in the dot dash square of FIG. 5. It will be understood that when the voltage across the capacitor is high the current through the thermionic diode 21a will be high, providing a more rapid decay rate than when the voltage is low. This, too, will provide differential decay rates.

In FIG. 6 the switch 5 is shown as operated by a play ing key 23. The R.F. source is shown as comprising a double triode thermionic tube 24. The first section of this tube and its circuitry constitute a Hartley oscillator having a tank circuit comprising a capacitor 25 and an inductance 26. The grid of the first section of the tube is biased through the usual parallel combination of resistor 27 and capacitor 28. The cathode of the first section of the tube is connected to a tap on inductance 26.

The second section of the tube 24 and its associated circuitry constitutes a cathode follower butter amplifier the purpose of which is to provide a low impedance RF. output. It will be noted that the grid of the second section is connected to the cathode of the first section through a capacitor 29. Grid bias is furnished through resistor 30. The plates of the two tube sections are connected together as shown and to a source of B+ potential. The cathode circuit of the second tube section contains a resistor 31 and capacitor 32 in parallel connected to the common return through an inductance 33. The RF. frequency take-oil occurs above the inductance.

An inductance 34 tunes out the residual capacity between the RF. electrode in the valve tube 2 and the external electrode 11, thus allowing a greater modulation of the RF. signal.

The first section of a dual thermionic triode 35 and its associated circuitry serves as a detector. The grid of the first section is connected to the external electrode 11 through a parallel resistor and capacitor 36 and 37. An inductance 3S tunes the grid leak detector to the R.F. signal. The plate or" the first section is connected to the 13-}- source through a resistor 36a. The second section of the tube 35 and its associated circuitry operates as a cathode follower amplifier stage; but between this and the detector it is preferable to locate an RF. filter comprising capacitors 39, it) and 41 and resistors 42 and 43. Grid bias is derived from a circuit containing resistors 42 and 44. The cathode follower resistor is indicated at 45. The AP. signal is derived from the cathode through a coupling capacitor as. In FIG. 6 there is shown a plurality of tone color filters 22 and 22a connected between the amplifier stage and the output system 7 through stop tab operating switches 4'7 and 48.

In FIG. 7, connections from a plurality of AF. generators 1 and 1a are shown. Each of these connections includes a switch operated by a different playing key 23 or 23a. Gradual tone decay on the release of keys 23 or 23a is accomplished by capacitors 1.8 and 18a which discharge through resistors 88 to the volt bus 89. This type decay circuit is more simplified than the double decay circuit of FIG. 5a, but it provides an acceptable decay with a minimum number of components and a minimum value of capacity for capacitors l3 and 18a. FIG. 7 indicates that a single source 4 of D.C. potential will serve for all the valves through a bus d9. Likewise source 9'0 serves all valves through bus 89. Each generator has its own electronic valve 2, 241, etc.

A double triode tube is shown at 50. The first section of this tube constitutes a tuned grid RF. oscillator having a tank circuit comprising capacitor 51 and inductance 52. The grid bias elements for the first section of tube are made up of capacitor 53 and resistor 54. The capacitor 53 is large enough to pass the audio signal. Plate feed-back is accomplished through inductance 55 6 coupled to inductance 52. FIG. 7 shows that the R.F. oscillator can feed all of the electronic valves 2, 2a, etc.

When the key switch 5 is closed by key 23 and the neon tube 2 is rendered conductive, a load is placed on the RF. oscillator which will vary in accordance with the AF. signal from generator 1. This produces amplitude modulation in the grid circuit of the RF. source. By proper adjustment of the grid leak bias components 53 and 5 this modulation is detected in the plate circuit of the oscillator tube. Due to the presence of resistor se in the plate circuit, a detected audio signal output is provided by the oscillating detector at the junction of the inductance 55 and the resistor 56. It will be understood that if one or more other key switches such as 5a are simultaneously closed the RF. signal will be modulated by two or more A.F. signals produced by different generators.

In FIG. 7 the second section of the tube 50 and its associated circuitry is an amplifier for the AF. signal; and the AF. signal is imposed on the grid of the amplifier through a filter comprising capacitors 57, 5d and 5% and resistors as and 61. In this instance the filter serves in conjunction with the oscillating detector and bypasses the bulk of the Rf. portion of the signal to ground while allowing the audio signal to pass undisturbed. The usual resistor 62 and capacitor 63 in parallel are connected between the cathode of a second section of the tube and ground. The output is taken from the plate through a coupling capacitor 64. The usual plate resistor 65 is connected between the plate and the B-{- source. Additional RF. filtering is accomplished by capacitor es.

FIG. 9 shows an exemplary system involving a plurality of oscillators and their gating circuits, and illustrates the derivation of octavely related tones in different headers, and the derivation of tone colors from oscillations in any one header or combination of headers and by outphasing, all as is taught in the Flock Patent 2,233,948. Certain oscillators are shown in FIG. 9 labeled respectively C C C and C It will be understood that C and C for example, are octavely related generators. Again, like index numerals have been used to designate like parts. It will be noted that generator C is connected through capacitor 8 and resistor 9 to electronic valve 2. There is a single source of DC. potential 4 which feeds all of the key switches through a bus 49. There is a single RF. source 3 which feeds all of the electronic valves through a header 67. The external electrode 11 of electronic valve 2 is connected to a header 68 which is an 3 header. When the key switch 5 is closed by the key 23 a signal from generator C will be derived in the header 6% because the electronic valve 2 will be actuated by the R.F., AF. and DC. voltages. FIG. 9 illustrates the same means for obtaining a differential decay rate as has been described in connection with FIG. 5. This means does not need redescription; but it may be noted that there is a switch 69 in the circuit of capacitor 18 and its associated decay components. This switch is connected with other switches (such as 69:!) similarly located in the circuits of other generators. These switches may be coupled together by means diagrammatically indicated at 7t? and operated by a stop tab. The means 7t? may also be a multi-contact relay operated by a stop tab. Either of these arrangements will enable the operator of the instrument to obtain the dual decay effect or an abrupt cessation of the tone at his option. In a somewhat more elaborated system a similar series of switches could be located in that branch of each of the circuits which contains the neon tube 21. Thus the operator may have available to him a selection of rates of decay as well as an abrupt cessation of the tone.

A second valve 2a is shown in FIG. 9 as having a connection through a resistor 9a and a lead 71 containing a capacitor 8b to the C oscillator. The external electrode 11a is shown as connected to a header '72 which is a 4' header. Since the lead '71 is connected to the switchS through a resistor 73, it will be evident that when switch 5 is closed valve 2a will fire simultaneously with valve 2 and that oscillations from two different harmonically related generators will be simultaneously derived in headers 63 and '72 despite the fact that key 23 operates only one switch 5. This is a further aspect of economy in the system of this invention.

Tracing the circuit shown in FIG. 9, one will see how upon the closure of switch 5a harmonically related tones from generators Cit, and C2 will be simultaneously de rived in headers 58 and 72. The skilled worker in the art will further understand that additional headers may be provided for other harmonically related tones if desired, and these tones derived in various headers, still with the use of only one simple make-and-break switch beneath each key. It will also be understood that the bank of generators of which C etc. are a part can be used to feed other divisions of the organ.

In FIG. 9 a detector '74 (which may include a filter and amplifier) is shown connected between the header 72 and a supplementary 4 header '75 which feeds tone color filters 76 and 77 for the derivation of 4 voices. Similarly a detector 78 is shown connected between header 68 and a supplementary 8 header '79 to which are connected filter circuits 8!! and 8.1. for the derivation of 8 voices. Headers 75' and 79 are shown connected to a filter circuit 82 for the derivation of a mixed voice such as a diapason. A filter 83 is shown connected to the 8' header '79 and also the 4' header 75, the latter connection being through an outphaser 84 as described in the Keck patent referred to above. The mixture of harmonically related tones in out of phase relationship in the filter 83 will give a voice in which the odd order harmonics are accentuated, e.g., a woodwind voice.

FIG. 9 also shows an alternate form of source detection, where a mesh 91, tuned to the frequency of the source 3 is inductivity coupled to the line d2 feeding the neon tubes 2, 2a, etc. The audio frequency variations in the line 92 are then detected by a diode 93 and passed through filter amplifier in, a mixture tone color filter 85, and stop switch 94, to the output system 87. Thus, it will be realized, harmonically related oscillations may be used for mixture voices, with little added complication to the system, by the use of a common RF. source.

Stop switches are indicated at 47, 48 and elsewhere, the filter circuits being shown as feeding a collector 86 which in'turn feeds the output 8-7, consisting generally of a main amplifier, volume control means and one or more loudspeakers, although other elements may be in cluded if desired.

Because of the high-audio-impedance characteristics of the RF. circuitry, the system of this invention eliminates feed-through. Since a single source of DC. potential and a single RF. source may be used, the gating means become matters of simple and inexpensive circuitry. The electronic valves are themselves simple and inexpensive, and only one switch need to be used beneath each playing key, the switch being of the simple make-and-break type. Thus the system is cost compares favorably with gradual contact switches and present various advantages thereof. One of these advantages lies in the simplicity of the means of obtaining percussive efiects where desired.

Modifications may be made in the invention without departing from the spirit of it. The invention having been described in certain exemplary embodiments, what is claimed as new and desired to be secured by Letters Patent is:

1. In an organ keying system for tone signal, a source of said tone signal, a source of carrier signal, a normally inoperative modulator, means applying said tone signal and said carrier signal continuously to said normally inoperative modulator for modulation of said carrier signal by saidtone signal when said modulator becomes operative, key operated switch means operative at will for rendering said modulator operative, whereby said carrier signal is modulated by said tone signal to provide a modulated carrier signal, and detection means responsive to said modulated carrier signal for deriving said tone signal from said modulated carrier signal, and means coupled to said detector means for acoustically radiating said tone signal.

2. In an organ system for keying tone signal, a source of tone signal; a source of carrier signal, a modulating circuit including a modulating diode, said diode being nonconductive to said tone signal and carrier signal in absence of an excitation signal applied to said modulating circuit, means applying said tone signal and said carrier signal continuously to said diode, a source of said excitation signal capable of rendering said diode conductive when applied to said diode, organ keying means for at will applying said excitation signal to said diode and With-drawing said excitation signal from said diode, whereby said diode modulates said carrier signal with said tone signal to provide a modulated carrier signal, and means coupled to said modulating diode for deriving the tone signal only from modulated carrier signal as a detected audio signal and means for acoustically radiating the desire-cl tone signal.

3. The combination according to claim 2 wherein said excitation signal is a direct current signal.

4. The combination according to claim 3 wherein are provided means for controlling the growth and decay of said direct current signal on application and withdrawal thereof from said diode, whereby the detected tone signal is provided with a controlled envelope.

5. The'combination according to claim 4 wherein said means for controlling includes a combination of capacitor and resistance in circuit with said direct current signal.

6. A tone keying circuit for an electric organ comprising:

(a) a normally non-conductive modulating electronic valve,

(b) a source of tone frequency modulating signal,

(c) a source of carrier signal,

(d) means for coupling said sources to said valve, said sources providing said tone frequency signal and said carrier signal simultaneously to said valve at amplitudes inadequate to render said valve conductive,

(e) a source of exciting signal of amplitude adequate to render said valve conductive,

f) organ keying means for at will applying said exciting signal to said valve for rendering said valve conductive, whereby said carrier signal is modulated by said audio frequency modulating signal on actuation of said keying means to provide a modulated carrier signal, and

(g) means coupled to said valve for deriving said tone frequency signal only from the modulated carrier signal.

7. An organ tone keying circuit comprising:

(a) a normally non-conductive modulating electronic valve having at least two electrodes,

(b) first circuit means coupled to at least one of said electrodes for continuously applying organ tone signal thereto,

(0) second circuit means coupled to at least one of said electrodes for continuously applying radio frequency voltage thereto, said valve being substantially non-conductive in response only to said organ tone signal and said radio frequency voltage applied to said at least one of said electrodes,

(d) an excitation source, and

(e) key operated switchmeans in series with said excitation source for at will coupling said excitation source to at least one of said electrodes, said electronic valve being rendered conductive in response to said excitation and providing an organ tone modulated carrier, and

(f) means coupled to said valve for deriving said organ tone signal only from the modulated carrier.

8. The combination according to claim 7 wherein said excitation source is a source of direct current voltage.

9. The combination according to claim 7 wherein said organ tone signal and said radio frequency voltage are applied to dilferent electrodes of said electronic valve.

Ill. The combination according to claim 7 wherein said electronic valve is a gaseous conduction device.

11. The combination according to claim 7 wherein said electronic valve is a gaseous diode.

12. In an organ system, a plurality of octavely related audio oscillators each providing a musical tone, a plurality of discrete heaters of different footages, separate electronic gates connecting individual ones of said audio ocillators to plural ones of said headers, said electronic gates being each normally non-conductive and being arranged to be rendered conductive in response to application of direct current gating voltage, a plurality of keys, a single source of said gating voltage, and gating circuits responsive to actuation of each individual key for applying said gating voltage jointly to render selected ones of said gates conductive to convey octavely related ones of said tones simultaneously to different ones of said headers.

13. The combination according to claim 12 wherein is further provided individual sustain circuits each operative concurrently to sustain octavely related ones of said tones deriving from octavely related ones of said audio oscillators and conveyed to different ones of said headers, said single sustain circuit being connected intermediate said single source of gating voltage and said gating circuits, and means for at will disabling all said sustain circuits.

14. In an organ system, a C tone oscillator, a C tone oscillator, where C and C are audio tones appropriate to two successive octaves of the musical scale and having frequencies appropriate to tones of musical nomenclature C, and A header, a B header, a first gating circuit converting the C oscillator to the A header, a second gating circuit connecting the C oscillator to the A header, a third gating circuit connecting the C oscillator to the B header, a fourth gating circuit connecting the C oscillator to the B header, each of said gating circuits being normally non-conductive and being individually rendered conductive responsive to application of direct current gating voltage, a single source of said gating voltage, a first C key, a second C key, means responsive to depression of said first C key for applying said gating voltage jointly to said first and third gating circuits, and means responsive to depressionof said second C key for applying said gating voltage jointly to said second and fourth gating circuit, wherein A and B are different footages.

15. The combination according to claim 14 wherein is further provided single sustain circuit means associated with each individual one of said keys for jointly providing selective sustain to both said B and said A header on depression of an individual one of said keys.

16. A circuit for keying tones of an electric organ comprising a modulator electronic valve having at least two electrodes, a continuously-running organ tone signal modulating source continuously coupled between one of said electrodes and a common return path, a continuouslyrunning carrier source continuously coupled between the other of said electrodes and said common return path, said valve being substantially non-conductive in response to the audio signal provided by said organ tone signal modulating source and the carrier provided by said carrier source alone and being capable of conducting and modulating only in response to an additional adequate excitation voltage applied across said electrodes, a source of said excitation voltage, key operated switch means for connecting and thereafter disconnecting said source of excitation voltage between one electrode of said valve and said common return path at will, whereby said valve conducts and modulates to provide said carrier modulated by said organ tone signal as a modulated carrier and means coupled to said modulator electronic valve for deriving said organ tone signal only from the modulated carrier.

17. A keying circuit for an electric organ comprising a modulating electronic valve having at least two electrodes, a continuously running musical tone signal source having a first terminal coupled to one electrode of said modulating electronic valve and a second terminal connected to a common return path, a continuously running radio frequency voltage source having a first terminal coupled to the other electrode of said modulating electronic valve and a second terminal connected to said common return path, said modulating electronic valve being substantially nonconductive and incapable of modulating in response to the musical tone signal and said radio frequency voltage provided by said musical tone signal source and said radio frequency voltage source during the concurrent absence of direct keying voltage applied across only said electrodes, a source of said direct control voltage, key operated switching means connecting said source of direct control voltage between one electrode of said modulating electronic valve and said common return path, and detector means coupled to said modulating electronic valve for deriving said musical tone signal only from modulated radio frequency voltage provided by said modulating electronic valve.

18. A keying circuit for an electronic organ comprising a musical tone signal source, a carrier source, there being a common return path between said musical tone signal source and said carrier source, an electronic modulator valve coupled between said sources, said electronic modulator valve being normally substantially non-conductive and incapable of modulating but capable of being rendered conductive and of modulating musical tone signal derived from said musical tone signal source on carrier derived from said carrier source upon the application of sufiicient direct control potential to said electronic modulator valve, thereby to provide a modulated carrier, a source of said suflicient direct control potential, and key operated switch means connecting said source of said control potential between said valve and said common return path, whereby to render said electronic modulator valve conductive and capable of modulating upon actuation of said key operated switch means, and detector means coupled to said electronic modulator valve for deriving said musical tone signal from the modulated carrier only while said electronic modulator valve is conductive and modulating, and an electroacoustic radiator coupled in driven relation to said detection means.

19. In an electronic musical instrument of the type having a plurality of sources of audio frequency signal corresponding to notes of the musical scale, an output system for converting selected frequency audio signals derived from said sources and applied to said output system to audible sound, and a plurality of selective keying means for selecting audio frequency signal deriving from selected ones of said plurality of sources, the combination of means providing a carrier signal, a plurality of normally inoperative modulators, separate ones of said modulators being associativcly related to separate ones of said sources of audio frequency signal, means continuously applying said carrier signal simultaneously to all of said plurality of modulators, means continuously applying said audio frequency signals derived from said plurality of sources of audio frequency signal to said associatively related modulators on a one for one basis, means for selectively rendering said normally inoperative modulators operative only in response to selective actuation of said keying means, whereby audio frequency signals provided by said source are selected for modulating said carrier signal to provide modulated carrier signal, means coupled to said plurality of normally inoperative modulators and responsive to the modulated carrier signal for deriving replicas of the selected audio frequency signals therefrom and means applying said replicas of the selected audio fre 'quency signals to said output system for conversion to 22. The combination according to claim 21 wherein said means for selectively rendering said normally inoperative modulators operative further includes a plurality of switch means, separate ones of said plurality of switch means being associatively related to separate ones of said modulators and to separate ones of said keying'means, said switch means being rendered operative to provide a conductive path for said excitation signal to said associatively related normally inoperative modulators in response to selected actuation of said keying means.

23. The combination according to claim 22 wherein said excitaton signal is a direct current signal.

24. The combination according to claim 23 wherein are provided means for controlling the growth and decay of said direct current signal on application and withdrawal thereof from said modulator whereby the replicas of the selected audio frequency signals are provided with a controlled envelope.

2 5. The combination according to claim 24 wherein said means for controlling includes resistive means and capacitive means operatively associated to provide time constants for controlling said growth and decay of said direct current signal, said means for controlling being con- 12 nected in shunt with said single source of excitation signal upon operation of said switch means.

References Cited by the Examiner UNITED STATES PATENTS 1,312,433 8/1919 Carson 33243 1,416,077 5/1922 Tanner 33252 1,996,359 4/1935 Whitaker 315174 2,481,608 9/1949 McKellip 84-l.26 X 2,483,823 10/1949 George 8'41 26 2,557,133 6/1951 Mork 841.19 X 2,745,011 5/1956 Bellows 33 l78 2,750,455 6/1956 Geisler 330-10 2,811,069 10/1957 Faulkner 84-101 3,040,612 6/1962 Dorf 84'--1.01 X

FOREIGN PATENTS 747,873 4/ 1956 Great Britain.

OTHER REFERENCES General Electric Transistor Manual, 2nd ed., received P.O., Apr. 1, 1958 (pages 98, 99 relied on).

Seright: Modulation Measurement, Electronics (mag azine), August, 1936 (pages 23 and 24 relied on).

Terman: Electronic and Radio Engineering, 4th ed., 1955, McGraw-Hill (page 721);

ARTHUR GAUSS, Primary Examiner.

CARL W. ROBINSON, Examiner.

Disclaimer 3,233,031.--Walter Munch, J12, Covington, Ky., and Robert 0. Sohere'r, Cincinnati, Ohio. GATING CIRCUITS FOR ELECTRICAL MUSI- CAL INSTRUMENTS. Patent dated Feb. 1, 1966. Disclaimer filed Oct. 1, 1973, by the assignee, D. H. Baldwin Company. Hereby enters this disclaimer to claims 12, 13, 14 and 15 of said patent.

[Ofim'al Gazette January 8,1974] 

19. IN AN ELECTRONIC MUSICAL INSTRUMENT OF THE TYPE HAVING A PLURALITY OF SOURCES OF AUDIO FREQUENCY SIGNAL CORRESPONDING TO NOTES OF THE MUSICAL SCALE, AN OUTPUT SYSTEM FOR CONVERTING SELECTED FREQUENCY AUDIO SIGNALS DERIVED FROM SAID SOURCES AND APPLIED TO SAID OUTPUT SYSTEM TO AUDIBLE SOUND, AND A PLURALITY OF SELECTIVE KEYING MEANS FOR SELECTING AUDIO FREQUENCY SIGNAL DERIVING FROM SELECTED ONES OF SAID PLURALITY OF SOURCES, THE COMBINATION OF MEANS PROVIDING A CARRIER SIGNAL, A PLURALITY OF NORMALLY INOPERATIVE MODULATORS, SEPARATE ONES OF SAID MODULATORS BEING ASSOCIATIVELY RELATED TO SEPARATE ONES OF SAID SOURCES OF AUDIO FREQUENCY SIGNAL, MEANS CONTINUOUSLY APPLYING SAID CARRIER SIGNAL SIMULTANEOUSLY TO ALL OF SAID PLURALITY OF MODULATORS, MEANS CONTINUOUSLY APPLYING SAID AUDIO FREQUENCY SIGNALS DERIVED FROM SAID PLURALITY OF SOURCES OF AUDIO FREQUENCY SIGNAL TO SAID ASSOCIATIVELY RELATED MODULATORS ON A ONE FOR ONE BASIS, MEANS FOR SELECTIVELY RENDERING SAID NORMALLY INOPERATIVE MODULATORS OPERATIVE ONLY IN RESPONSE TO SELECTIVE ACTUATING OF SAID KEYING 